Comparison of salivary antimicrobial peptides and upper respiratory tract infections in elite marathon runners and sedentary subjects

Abstract

The aim of the present study was to examine the relationship between human β-defensin-2 (HBD-2), cathelicidin (LL-37) and upper respiratory tract infections (URTI). In addition, the possible association between salivary cortisol and the salivary antimicrobial peptides was also examined. We hypothesized that the saliva levels of HBD-2 and LL-37 are lower in elite marathon runners; and that saliva cortisol levels might have a negative association with saliva HBD-2 and LL-37. Twenty elite male marathon runners were studied, and twenty additional male subjects were used as sedentary controls. Saliva samples were collected between 12:00 and 14:00 in the afternoon. We selected the cotton swab method of saliva collection. Elite marathon runners tend to have lower concentrations of salivary antimicrobial peptides (HBD-2 and LL-37) than sedentary subjects. Saliva cortisol levels in the elite marathon runners were significantly higher than those in the sedentary subjects. Concentration of saliva cortisol levels showed a negative correlation with saliva HBD-2 and saliva LL-37 concentration levels. Number of URTI in the elite marathon runners was significantly higher than in the sedentary subjects. Number of URTI was negatively correlated with saliva HBD-2 concentration and saliva LL-37 concentration levels. The present findings suggest the relationship between antimicrobial peptides and URTI in elite marathon runners and sedentary subjects. In addition, salivary antimicrobial peptides in the elite marathon runners were significantly lower than sedentary control subjects. It is possible that, while strenuous exercise in elite athletes could partly enhance oral innate immunity, the physical stress could simultaneously restrict the immunological enhancement due to HPA axis activity.

Keywords

• antimicrobial peptides
• human β-defensin-2
• ll-37
• cortisol
• upper respiratory infections